IMO C

my pick...D
a. experiencing-incorrect
b: experiencing-incorrect
c: that each experienced as a puppy- Yorkshire Terriers and a Jack Russell Terriers need plural puppies hence incorrect
d. that they experienced as puppies-correct
e.use of that had...... and when puppies-incorrect

@gmatrix

In option D will there not be a confusion as to what the "they" refers to: Yorkshire terriers or Jack Russell teriers??

OA pls

IMO D.

Interesting question. I believe that Yorkshire Terriers and Jack Russell Terriers constitute a compound subject within the clause "that even years later Yorkshire Terriers and Jack Russell Terriers will recognize scents experiencing when a puppy." As a compound subject I believe it functions as a single unit in which case "they" is appropriate.

Consider,

Tom and Bill went to the game. They had fun. (not, Each had fun)

Additionally, "will recognize" is a plural verb form. This also leads me to "they" rather than "each".

Never mind about "will recognize" being plural. But I still think it is D

kushal.adhia wrote:@gmatrix

In option D will there not be a confusion as to what the "they" refers to: Yorkshire terriers or Jack Russell teriers??

OA pls

hi.....imo C would be correct if the sentence read.......Levenstein asserts that even years later a Yorkshire Terrier and a Jack Russell Terrier will recognize scents that each experienced as a puppy

OA D

@ gmatrix and rkanthilal

got it. thanks for explaining =)